// proto: https://github.com/istio/api/blob/master/networking/v1alpha3/destination_rule.pb.go
package v1alpha3

import (
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
)

// +genclient
// +k8s:deepcopy-gen:interfaces=k8s.io/apimachinery/pkg/runtime.Object
// DestinationRule
type DestinationRule struct {
	metav1.TypeMeta   `json:",inline"`
	metav1.ObjectMeta `json:"metadata,omitempty"`
	Spec              DestinationRuleSpec `json:"spec"`
}

// DestinationRule defines policies that apply to traffic intended for a
// service after routing has occurred. These rules specify configuration
// for load balancing, connection pool size from the sidecar, and outlier
// detection settings to detect and evict unhealthy hosts from the load
// balancing pool. For example, a simple load balancing policy for the
// ratings service would look as follows:
//
//
// apiVersion: networking.istio.io/v1alpha3
// kind: DestinationRule
// metadata:
//   name: bookinfo-ratings
// spec:
//   host: ratings.prod.svc.cluster.local
//   trafficPolicy:
//     loadBalancer:
//       simple: LEAST_CONN
//
//
// Version specific policies can be specified by defining a named
// subset and overriding the settings specified at the service level. The
// following rule uses a round robin load balancing policy for all traffic
// going to a subset named testversion that is composed of endpoints (e.g.,
// pods) with labels (version:v3).
//
//
// apiVersion: networking.istio.io/v1alpha3
// kind: DestinationRule
// metadata:
//   name: bookinfo-ratings
// spec:
//   host: ratings.prod.svc.cluster.local
//   trafficPolicy:
//     loadBalancer:
//       simple: LEAST_CONN
//   subsets:
//   - name: testversion
//     labels:
//       version: v3
//     trafficPolicy:
//       loadBalancer:
//         simple: ROUND_ROBIN
//
//
// **Note:** Policies specified for subsets will not take effect until
// a route rule explicitly sends traffic to this subset.
//
// Traffic policies can be customized to specific ports as well. The
// following rule uses the least connection load balancing policy for all
// traffic to port 80, while uses a round robin load balancing setting for
// traffic to the port 9080.
//
//
// apiVersion: networking.istio.io/v1alpha3
// kind: DestinationRule
// metadata:
//   name: bookinfo-ratings-port
// spec:
//   host: ratings.prod.svc.cluster.local
//   trafficPolicy: # Apply to all ports
//     portLevelSettings:
//     - port:
//         number: 80
//       loadBalancer:
//         simple: LEAST_CONN
//     - port:
//         number: 9080
//       loadBalancer:
//         simple: ROUND_ROBIN
//
type DestinationRuleSpec struct {
	// REQUIRED. The name of a service from the service registry. Service
	// names are looked up from the platform's service registry (e.g.,
	// Kubernetes services, Consul services, etc.) and from the hosts
	// declared by [ServiceEntries](#ServiceEntry). Rules defined for
	// services that do not exist in the service registry will be ignored.
	//
	// *Note for Kubernetes users*: When short names are used (e.g. "reviews"
	// instead of "reviews.default.svc.cluster.local"), Istio will interpret
	// the short name based on the namespace of the rule, not the service. A
	// rule in the "default" namespace containing a host "reviews will be
	// interpreted as "reviews.default.svc.cluster.local", irrespective of
	// the actual namespace associated with the reviews service. _To avoid
	// potential misconfigurations, it is recommended to always use fully
	// qualified domain names over short names._
	//
	// Note that the host field applies to both HTTP and TCP services.
	Host string `json:"host"`

	// Traffic policies to apply (load balancing policy, connection pool
	// sizes, outlier detection).
	TrafficPolicy *TrafficPolicy `json:"trafficPolicy,omitempty"`

	// One or more named sets that represent individual versions of a
	// service. Traffic policies can be overridden at subset level.
	Subsets []Subset `json:"subsets,omitempty"`
}

// Traffic policies to apply for a specific destination, across all
// destination ports. See DestinationRule for examples.
type TrafficPolicy struct {

	// Settings controlling the load balancer algorithms.
	LoadBalancer *LoadBalancerSettings `json:"loadBalancer,omitempty"`

	// Settings controlling the volume of connections to an upstream service
	ConnectionPool *ConnectionPoolSettings `json:"connectionPool,omitempty"`

	// Settings controlling eviction of unhealthy hosts from the load balancing pool
	OutlierDetection *OutlierDetection `json:"outlierDetection,omitempty"`

	// TLS related settings for connections to the upstream service.
	TLS *TLSSettings `json:"tls,omitempty"`

	// Traffic policies specific to individual ports. Note that port level
	// settings will override the destination-level settings. Traffic
	// settings specified at the destination-level will not be inherited when
	// overridden by port-level settings, i.e. default values will be applied
	// to fields omitted in port-level traffic policies.
	PortLevelSettings []PortTrafficPolicy `json:"portLevelSettings,omitempty"`
}

// Traffic policies that apply to specific ports of the service
type PortTrafficPolicy struct {
	// Specifies the port name or number of a port on the destination service
	// on which this policy is being applied.
	//
	// Names must comply with DNS label syntax (rfc1035) and therefore cannot
	// collide with numbers. If there are multiple ports on a service with
	// the same protocol the names should be of the form <protocol-name>-<DNS
	// label>.
	Port PortSelector `json:"port"`

	// Settings controlling the load balancer algorithms.
	LoadBalancer *LoadBalancerSettings `json:"loadBalancer,omitempty"`

	// Settings controlling the volume of connections to an upstream service
	ConnectionPool *ConnectionPoolSettings `json:"connectionPool,omitempty"`

	// Settings controlling eviction of unhealthy hosts from the load balancing pool
	OutlierDetection *OutlierDetection `json:"outlierDetection,omitempty"`

	// TLS related settings for connections to the upstream service.
	TLS *TLSSettings `json:"tls,omitempty"`
}

// A subset of endpoints of a service. Subsets can be used for scenarios
// like A/B testing, or routing to a specific version of a service. Refer
// to [VirtualService](#VirtualService) documentation for examples of using
// subsets in these scenarios. In addition, traffic policies defined at the
// service-level can be overridden at a subset-level. The following rule
// uses a round robin load balancing policy for all traffic going to a
// subset named testversion that is composed of endpoints (e.g., pods) with
// labels (version:v3).
//
// apiVersion: networking.istio.io/v1alpha3
// kind: DestinationRule
// metadata:
//   name: bookinfo-ratings
// spec:
//   host: ratings.prod.svc.cluster.local
//   trafficPolicy:
//     loadBalancer:
//       simple: LEAST_CONN
//   subsets:
//   - name: testversion
//     labels:
//       version: v3
//     trafficPolicy:
//       loadBalancer:
//         simple: ROUND_ROBIN
//
// **Note:** Policies specified for subsets will not take effect until
// a route rule explicitly sends traffic to this subset.
type Subset struct {
	// REQUIRED. Name of the subset. The service name and the subset name can
	// be used for traffic splitting in a route rule.
	Name string `json:"name"`

	// REQUIRED. Labels apply a filter over the endpoints of a service in the
	// service registry. See route rules for examples of usage.
	Labels map[string]string `json:"labels"`

	// Traffic policies that apply to this subset. Subsets inherit the
	// traffic policies specified at the DestinationRule level. Settings
	// specified at the subset level will override the corresponding settings
	// specified at the DestinationRule level.
	TrafficPolicy *TrafficPolicy `json:"trafficPolicy,omitempty"`
}

// Load balancing policies to apply for a specific destination. See Envoy's
// load balancing
// [documentation](https://www.envoyproxy.io/docs/envoy/latest/intro/arch_overview/load_balancing.html)
// for more details.
//
// For example, the following rule uses a round robin load balancing policy
// for all traffic going to the ratings service.
//
// apiVersion: networking.istio.io/v1alpha3
// kind: DestinationRule
// metadata:
//   name: bookinfo-ratings
// spec:
//   host: ratings.prod.svc.cluster.local
//   trafficPolicy:
//     loadBalancer:
//       simple: ROUND_ROBIN
//
// The following example sets up sticky sessions for the ratings service
// hashing-based load balancer for the same ratings service using the
// the User cookie as the hash key.
//
//  apiVersion: networking.istio.io/v1alpha3
//  kind: DestinationRule
//  metadata:
//    name: bookinfo-ratings
//  spec:
//    host: ratings.prod.svc.cluster.local
//    trafficPolicy:
//      loadBalancer:
//        consistentHash:
//          httpCookie:
//            name: user
//            ttl: 0s
type LoadBalancerSettings struct {
	// It is required to specify exactly one of the fields:
	// Simple or ConsistentHash
	Simple         SimpleLB          `json:"simple,omitempty"`
	ConsistentHash *ConsistentHashLB `json:"consistentHash,omitempty"`
}

// Standard load balancing algorithms that require no tuning.
type SimpleLB string

const (
	// Round Robin policy. Default
	SimpleLBRoundRobin SimpleLB = "ROUND_ROBIN"

	// The least request load balancer uses an O(1) algorithm which selects
	// two random healthy hosts and picks the host which has fewer active
	// requests.
	SimpleLBLeastConn SimpleLB = "LEAST_CONN"

	// The random load balancer selects a random healthy host. The random
	// load balancer generally performs better than round robin if no health
	// checking policy is configured.
	SimpleLBRandom SimpleLB = "RANDOM"

	// This option will forward the connection to the original IP address
	// requested by the caller without doing any form of load
	// balancing. This option must be used with care. It is meant for
	// advanced use cases. Refer to Original Destination load balancer in
	// Envoy for further details.
	SimpleLBPassthrough SimpleLB = "PASSTHROUGH"
)

// Consistent Hash-based load balancing can be used to provide soft
// session affinity based on HTTP headers, cookies or other
// properties. This load balancing policy is applicable only for HTTP
// connections. The affinity to a particular destination host will be
// lost when one or more hosts are added/removed from the destination
// service.
type ConsistentHashLB struct {

	// It is required to specify exactly one of the fields as hash key:
	// HTTPHeaderName, HTTPCookie, or UseSourceIP.
	// Hash based on a specific HTTP header.
	HTTPHeaderName string `json:"httpHeaderName,omitempty"`

	// Hash based on HTTP cookie.
	HTTPCookie *HTTPCookie `json:"httpCookie,omitempty"`

	// Hash based on the source IP address.
	UseSourceIP bool `json:"useSourceIp,omitempty"`

	// The minimum number of virtual nodes to use for the hash
	// ring. Defaults to 1024. Larger ring sizes result in more granular
	// load distributions. If the number of hosts in the load balancing
	// pool is larger than the ring size, each host will be assigned a
	// single virtual node.
	MinimumRingSize uint64 `json:"minimumRingSize,omitempty"`
}

// Describes a HTTP cookie that will be used as the hash key for the
// Consistent Hash load balancer. If the cookie is not present, it will
// be generated.
type HTTPCookie struct {
	// REQUIRED. Name of the cookie.
	Name string `json:"name"`

	// Path to set for the cookie.
	Path string `json:"path,omitempty"`

	// REQUIRED. Lifetime of the cookie.
	TTL string `json:"ttl"`
}

// Connection pool settings for an upstream host. The settings apply to
// each individual host in the upstream service.  See Envoy's [circuit
// breaker](https://www.envoyproxy.io/docs/envoy/latest/intro/arch_overview/circuit_breaking)
// for more details. Connection pool settings can be applied at the TCP
// level as well as at HTTP level.
//
// For example, the following rule sets a limit of 100 connections to redis
// service called myredissrv with a connect timeout of 30ms
//
// apiVersion: networking.istio.io/v1alpha3
// kind: DestinationRule
// metadata:
//   name: bookinfo-redis
// spec:
//   host: myredissrv.prod.svc.cluster.local
//   trafficPolicy:
//     connectionPool:
//       tcp:
//         maxConnections: 100
//         connectTimeout: 30ms
type ConnectionPoolSettings struct {

	// Settings common to both HTTP and TCP upstream connections.
	TCP *TCPSettings `json:"tcp,omitempty"`

	// HTTP connection pool settings.
	HTTP *HTTPSettings `json:"http,omitempty"`
}

// Settings common to both HTTP and TCP upstream connections.
type TCPSettings struct {
	// Maximum number of HTTP1 /TCP connections to a destination host.
	MaxConnections int32 `json:"maxConnections,omitempty"`

	// TCP connection timeout.
	ConnectTimeout string `json:"connectTimeout,omitempty"`
}

// Settings applicable to HTTP1.1/HTTP2/GRPC connections.
type HTTPSettings struct {
	// Specify if http1.1 connection should be upgraded to http2 for the associated destination.
	// DEFAULT - Use the global default.
	// DO_NOT_UPGRADE - Do not upgrade the connection to http2.
	// UPGRADE - Upgrade the connection to http2.
	H2UpgradePolicy string `json:"h2UpgradePolicy,omitempty"`

	// Maximum number of pending HTTP requests to a destination. Default 2^32-1.
	HTTP1MaxPendingRequests int32 `json:"http1MaxPendingRequests,omitempty"`

	// Maximum number of requests to a backend. Default 2^32-1.
	HTTP2MaxRequests int32 `json:"http2MaxRequests,omitempty"`

	// Maximum number of requests per connection to a backend. Setting this
	// parameter to 1 disables keep alive. Default 0, meaning "unlimited",
	// up to 2^29.
	MaxRequestsPerConnection int32 `json:"maxRequestsPerConnection,omitempty"`

	// Maximum number of retries that can be outstanding to all hosts in a
	// cluster at a given time. Defaults to 2^32-1.
	MaxRetries int32 `json:"maxRetries,omitempty"`

	// The idle timeout for upstream connection pool connections. The idle timeout is defined as the period in which there are no active requests.
	// If not set, the default is 1 hour. When the idle timeout is reached the connection will be closed.
	// Note that request based timeouts mean that HTTP/2 PINGs will not keep the connection alive. Applies to both HTTP1.1 and HTTP2 connections.
	IdleTimeout string `json:"idleTimeout,omitempty"`
}

// A Circuit breaker implementation that tracks the status of each
// individual host in the upstream service.  Applicable to both HTTP and
// TCP services.  For HTTP services, hosts that continually return 5xx
// errors for API calls are ejected from the pool for a pre-defined period
// of time. For TCP services, connection timeouts or connection
// failures to a given host counts as an error when measuring the
// consecutive errors metric. See Envoy's [outlier
// detection](https://www.envoyproxy.io/docs/envoy/latest/intro/arch_overview/outlier)
// for more details.
//
// The following rule sets a connection pool size of 100 connections and
// 1000 concurrent HTTP2 requests, with no more than 10 req/connection to
// "reviews" service. In addition, it configures upstream hosts to be
// scanned every 5 mins, such that any host that fails 7 consecutive times
// with 5XX error code will be ejected for 15 minutes.
//
// apiVersion: networking.istio.io/v1alpha3
// kind: DestinationRule
// metadata:
//   name: reviews-cb-policy
// spec:
//   host: reviews.prod.svc.cluster.local
//   trafficPolicy:
//     connectionPool:
//       tcp:
//         maxConnections: 100
//       http:
//         http2MaxRequests: 1000
//         maxRequestsPerConnection: 10
//     outlierDetection:
//       consecutiveErrors: 7
//       interval: 5m
//       baseEjectionTime: 15m
type OutlierDetection struct {
	// Number of errors before a host is ejected from the connection
	// pool. Defaults to 5. When the upstream host is accessed over HTTP, a
	// 5xx return code qualifies as an error. When the upstream host is
	// accessed over an opaque TCP connection, connect timeouts and
	// connection error/failure events qualify as an error.
	ConsecutiveErrors int32 `json:"consecutiveErrors,omitempty"`

	// Number of gateway errors before a host is ejected from the connection pool.
	// When the upstream host is accessed over HTTP, a 502, 503, or 504 return
	// code qualifies as a gateway error. When the upstream host is accessed over
	// an opaque TCP connection, connect timeouts and connection error/failure
	// events qualify as a gateway error.
	// This feature is disabled by default or when set to the value 0.
	//
	// Note that consecutive_gateway_errors and consecutive_5xx_errors can be
	// used separately or together. Because the errors counted by
	// consecutive_gateway_errors are also included in consecutive_5xx_errors,
	// if the value of consecutive_gateway_errors is greater than or equal to
	// the value of consecutive_5xx_errors, consecutive_gateway_errors will have
	// no effect.
	ConsecutiveGatewayErrors *uint32 `json:"consecutiveGatewayErrors,omitempty"`

	// Number of 5xx errors before a host is ejected from the connection pool.
	// When the upstream host is accessed over an opaque TCP connection, connect
	// timeouts, connection error/failure and request failure events qualify as a
	// 5xx error.
	// This feature defaults to 5 but can be disabled by setting the value to 0.
	//
	// Note that consecutive_gateway_errors and consecutive_5xx_errors can be
	// used separately or together. Because the errors counted by
	// consecutive_gateway_errors are also included in consecutive_5xx_errors,
	// if the value of consecutive_gateway_errors is greater than or equal to
	// the value of consecutive_5xx_errors, consecutive_gateway_errors will have
	// no effect.
	Consecutive5xxErrors *uint32 `json:"consecutive5xxErrors,omitempty"`

	// Time interval between ejection sweep analysis. format:
	// 1h/1m/1s/1ms. MUST BE >=1ms. Default is 10s.
	Interval string `json:"interval,omitempty"`

	// Minimum ejection duration. A host will remain ejected for a period
	// equal to the product of minimum ejection duration and the number of
	// times the host has been ejected. This technique allows the system to
	// automatically increase the ejection period for unhealthy upstream
	// servers. format: 1h/1m/1s/1ms. MUST BE >=1ms. Default is 30s.
	BaseEjectionTime string `json:"baseEjectionTime,omitempty"`

	// Maximum % of hosts in the load balancing pool for the upstream
	// service that can be ejected. Defaults to 10%.
	MaxEjectionPercent int32 `json:"maxEjectionPercent,omitempty"`

	// Outlier detection will be enabled as long as the associated load balancing
	// pool has at least min_health_percent hosts in healthy mode. When the
	// percentage of healthy hosts in the load balancing pool drops below this
	// threshold, outlier detection will be disabled and the proxy will load balance
	// across all hosts in the pool (healthy and unhealthy). The threshold can be
	// disabled by setting it to 0%. The default is 0% as it's not typically
	// applicable in k8s environments with few pods per service.
	MinHealthPercent int32 `json:"minHealthPercent,omitempty"`
}

// SSL/TLS related settings for upstream connections. See Envoy's [TLS
// context](https://www.envoyproxy.io/docs/envoy/latest/api-v1/cluster_manager/cluster_ssl.html#config-cluster-manager-cluster-ssl)
// for more details. These settings are common to both HTTP and TCP upstreams.
//
// For example, the following rule configures a client to use mutual TLS
// for connections to upstream database cluster.
//
// apiVersion: networking.istio.io/v1alpha3
// kind: DestinationRule
// metadata:
//   name: db-mtls
// spec:
//   host: mydbserver.prod.svc.cluster.local
//   trafficPolicy:
//     tls:
//       mode: MUTUAL
//       clientCertificate: /etc/certs/myclientcert.pem
//       privateKey: /etc/certs/client_private_key.pem
//       caCertificates: /etc/certs/rootcacerts.pem
//
// The following rule configures a client to use TLS when talking to a
// foreign service whose domain matches *.foo.com.
//
// apiVersion: networking.istio.io/v1alpha3
// kind: DestinationRule
// metadata:
//   name: tls-foo
// spec:
//   host: "*.foo.com"
//   trafficPolicy:
//     tls:
//       mode: SIMPLE
//
// The following rule configures a client to use Istio mutual TLS when talking
// to rating services.
//
// apiVersion: networking.istio.io/v1alpha3
// kind: DestinationRule
// metadata:
//   name: ratings-istio-mtls
// spec:
//   host: ratings.prod.svc.cluster.local
//   trafficPolicy:
//     tls:
//       mode: ISTIO_MUTUAL
type TLSSettings struct {

	// REQUIRED: Indicates whether connections to this port should be secured
	// using TLS. The value of this field determines how TLS is enforced.
	Mode TLSmode `json:"mode"`

	// REQUIRED if mode is `MUTUAL`. The path to the file holding the
	// client-side TLS certificate to use.
	// Should be empty if mode is `ISTIO_MUTUAL`.
	ClientCertificate string `json:"clientCertificate,omitempty"`

	// REQUIRED if mode is `MUTUAL`. The path to the file holding the
	// client's private key.
	// Should be empty if mode is `ISTIO_MUTUAL`.
	PrivateKey string `json:"privateKey,omitempty"`

	// OPTIONAL: The path to the file containing certificate authority
	// certificates to use in verifying a presented server certificate. If
	// omitted, the proxy will not verify the server's certificate.
	// Should be empty if mode is `ISTIO_MUTUAL`.
	CaCertificates string `json:"caCertificates,omitempty"`

	// A list of alternate names to verify the subject identity in the
	// certificate. If specified, the proxy will verify that the server
	// certificate's subject alt name matches one of the specified values.
	// Should be empty if mode is `ISTIO_MUTUAL`.
	SubjectAltNames []string `json:"subjectAltNames,omitempty"`

	// SNI string to present to the server during TLS handshake.
	// Should be empty if mode is `ISTIO_MUTUAL`.
	Sni string `json:"sni,omitempty"`
}

// TLS connection mode
type TLSmode string

const (
	// Do not setup a TLS connection to the upstream endpoint.
	TLSmodeDisable TLSmode = "DISABLE"

	// Originate a TLS connection to the upstream endpoint.
	TLSmodeSimple TLSmode = "SIMPLE"

	// Secure connections to the upstream using mutual TLS by presenting
	// client certificates for authentication.
	TLSmodeMutual TLSmode = "MUTUAL"

	// Secure connections to the upstream using mutual TLS by presenting
	// client certificates for authentication.
	// Compared to Mutual mode, this mode uses certificates generated
	// automatically by Istio for mTLS authentication. When this mode is
	// used, all other fields in `TLSSettings` should be empty.
	TLSmodeIstioMutual TLSmode = "ISTIO_MUTUAL"
)

// +k8s:deepcopy-gen:interfaces=k8s.io/apimachinery/pkg/runtime.Object
// DestinationRuleList is a list of DestinationRule resources
type DestinationRuleList struct {
	metav1.TypeMeta `json:",inline"`
	metav1.ListMeta `json:"metadata"`
	Items           []DestinationRule `json:"items"`
}
